Gamma-emitting receptor-binding 3-quinuclidinyl glycolates; methods of preparation thereof and imaging and assay methods utilizing same

ABSTRACT

Compounds of the formula: ##STR1## wherein R is aryl, alkyl, cycloalkyl, phenyl, cyclopentyl, cyclohexyl, a ligand containing Tc-99m in chelated form or a ligand capable of chelating Tc-99m; 
     R 1  is H or lower alkyl; 
     X is in the ortho-, meta or para- position, and is selected from the group consisting of  125  I,  123  I,  127  I, I,  18  F,  75  Br,  77  Br, NH 2 , and ##STR2## wherein R 2  is in the 2,3, or 4 position and is selected from the group consisting of H and lower alkyl, provided that when R is a ligand capable of chelating Tc-99m or containing Tc-99m in chelated form, X is not a radioisotope and may also be H or lower alkyl; 
     Z.sup.⊖ is an anion; or the free amine thereof; and 
     denotes an asymmetric carbon atom.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.156,106, filed June 3, 1980, now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to various muscarinic cholinergicreceptor-binding compounds, gamma-emitting radioisotope derivativesthereof, intermediate and methods for the production thereof and the useof the said radioisotope derivatives as radiopharmaceuticals in theassay and external imaging of myocardial tissue and other organscontaining muscarinic cholinergic receptors.

It is known that muscarinic cholinergic receptors are concentrated inmyocardial and other tissue. It is theorized that these receptors areinvolved in the action of drugs or biochemicals in the myocardial tissueand that changes in the concentration of the receptor in the myocardialtissue are a function of a disease state therein or in other tissuecontaining the receptors.

It has been established that various compounds function both in vitroand in vivo as muscarinic cholinergic receptor binders or antagonists.These compounds have a high affinity for and competitively bind with thereceptor. It has been established that various 3-quinuclidinylglycolates are effective muscarinic cholingergic receptor binders. Ithas further been suggested that tritium-labeled 3-quinuclidinylglycolates may be utilized as radiotracers for various assay proceduresinvolving myocardial tissue. See Eckelman et al, J. Nucl. Med., 20, 350(1979) and Gibson et al, J. Nucl. Med. 20, 865 (1979).

There are numerous disadvantages inherent in the use of tritium-labeledradiotracers. For example, numerous problems are associated with"counting" beta-emissions of tritium-labled compounds. Liquidscintillator must be added to each sample which is a time-consuming andexpensive procedure. Toluene is the typical scintillator liquid employedwhich is presently subject to strict, environmental sanctions because itis not miscible with water thereby rendering its disposal problematical.In addition, beta-counting procedures are plagued with problems ofchemluminescence and quenching which are absent in gamma-counting.

Tl-201 is presently employed for the detection and quantification ofmyocardial infarcts. However, the radiohalogens such as I-123 and Br-77have better imaging characteristics in that their higher gamma energiescan be detected with increased sensitivity and positional resolution ascompared with the lower gamma energy of Tl-201 (80 Ke V X-rays).

Since the size of the infarct is related to mortality and residualfunction, improved resolution will mean improved prognosis andevaluation of drug therapy. The radiohalogens F-18 and Br-75 arepositron emitters which offer the unique capabilities of resolution andquantification associated with such decay characteristics.

The unique radio imaging properties of Technetium-99m (Tc-99m) renderradio imaging and radio assay agents containing the Tc-99m radioisotopemore commercially viable than those agents containing otherradioisotopes. Tc-99m has become the radioisotope of choice because:

(1) It has a six hour half-life thereby rendering it most efficient asan external imaging agent.

(2) Unlike other radioisotopes used as radio-tracers, there is nobeta-component in the gamma-emission of Tc-99m.

(3) Technetium-99m is relatively inexpensive and widely available frommolybdenum generators.

(4) There is a low absorbed radiation dose connected with the use ofTc-99m.

It is an object of the present invention to provide various3-quinuclidinyl glycolates and gamma-emitting radioisotope containing3-quinuclidinyl glycolates useful for muscarinic cholinergic receptorassays, and imaging of the myocardium and in vitro muscariniccholinergic assay and tissue imaging techniques.

SUMMARY OF THE INVENTION

These and other objects of the present invention are achieved byproviding compounds of the formula: ##STR3## wherein R is aryl (e.g.,phenyl), alkyl, preferably lower alkyl, or cycloalkyl (e.g.,cyclopentyl, cyclohexyl); a ligand containing Tc-99m in chelated form ora ligand capable of chelating Tc-99m;

R₁ is H or lower alkyl, preferably CH₃ ;

X is in the ortho-, meta- or para-position, and is selected from thegroup consisting of ¹²⁵ I, ¹²³ I, ¹²⁷ I, I, 18_(F), 75_(Br), 77_(Br),NH₂, H, lower alkyl, and ##STR4## wherein R₂ is in the 2, 3, or 4position and is selected from the group consisting of H and alkyl,provided that, when R is a ligand capable of chelating Tc-99m orcontains Tc-99m in chelated form, X is H or lower alkyl; and n=3, 4, 5or 6;

Z.sup.⊖ is an anion; or the corresponding free amine, i.e., thenon-protonated or non-quaternary salt form; and

*denotes an asymmetric carbon atom.

The radio-labeled compounds are gamma-emitting and are useful informulating compositions suitable for in vitro assay of muscariniccholinergic receptors in, e.g., myocardial tissue and for formulatingcompositions suitable for use in external imaging or radio-assay ofmyocardial tissue and other tissues containing muscarinic cholinergicreceptors.

The derivatives wherein X is H, lower alkyl, halogen, amino- andtriazeno- are valuable as intermediates in the preparation of theradio-labeled analogs.

DETAILED DESCRIPTION OF THE INVENTION

The 4-aminobenzil may be prepared according to the method of Augl et al,Annu. Conf., SPE, Reinf. Plastic/Compos. Div. Proc., 26th, 19D, 1(1971). The 4-aminobenzil is rearranged to yield 4-aminobenzilic acidwhich is in turn esterfied to produce the ethyl ester. The ethyl esterof the 4-aminobenzilic acid is then reacted with quinuclidin-3-ol togive the expected 3-quinuclidinyl 4-aminobenzilate (4-amino-QNB). Thepurified 4-amino-QNB is then converted to the 4-triazeno-QNB accordingto the procedure reported by Tewson et al, J. Nucl. Med. 20, 671 (1979).The purified 4-triazeno-QNB is then reacted with iodide or a desiredgamma-emitting radionuclide to produce the desired product.

In the above structural formula the anion Z.sup.⊖ may be anypharmaceutically acceptable anion such as Cl⁻, Br⁻, or I⁻, SO₄ ⁼, HCOO⁻,CH₃ COO⁻, etc.

The compounds of the invention each possess two asymmetric carbon atomsin the quinuclidinyl glycolate moiety. It has been found that theactivity of the compounds as muscarinic cholinergic receptor-bindersdepends upon the absolute configuration of the C* atoms in the abovestructural formula. Although the S, S; R, S and S, R-isomers and theracemic diastereomeric mixture are active, the R, R configuration ismore highly active in most instances. Accordingly, it is preferred toutilize the R, R-isomer (i.e., at the C* atoms in the above structuredformula) in the invention described herein.

The following examples illustrate the preparation of the claimedcompounds.

EXAMPLE 1 4-Aminobenzilic Acid

A solution of 25 g of NaOH in 50 ml of H₂ O was placed in a water bathkept at 95° C. To this magnetically stirred solution was added 11.26 g(50 mmol) of 4-aminobenzil in small portions. After the addition wascompleted the mixture was stirred for 5 hours at 95° C. Water was addedduring the reaction to maintain the volume at about 100 ml. After 5hours the heating was discontinued and the reaction mixture wastransferred to a separatory funnel and extracted twice with 50 ml ofethyl ether. The aqueous layer was cooled to 0° acidified with conc. H₂SO₄ until turbid, and extracted with ethyl acetate (AcOEt) (100 ml). Theaqueous layer was acidified and extracted with AcOEt again. The combinedAcOEt layers were washed with water (2×), dried over MgSO₄, filtered andspin evaporated in vacuum. Thus obtained precipitate was recrystallizedfrom water/acetone 25/75. Yield 8.9 g (73 %). Yellow crystals, mp dec.150° C.; Silica gel TLC in acetone, Rf 0.25; HPLC Bondapak μC₁₈ inMeOH/H₂ O (75/25) pH 4 (formic acid). IR, UV, mass spec. were consistentwith the structure. Elemental Analysis calc for C₁₄ H₁₃ NO₃.2/3 H₂ O,calc. C 67.28, H 5.78, N 5.60; Found C 67.45, 67.64, H 5.49, 5.41, N5.52, 5.51.

EXAMPLE 2 4-Aminobenzilic Acid Ethyl Ester

4.8 g (19.7 mmol) of 4-aminobenzilic acid was dissolved in 200 ml ofabsolute ethanol (EtOH) saturated with dry HCl gas. The reaction mixturewas refluxed for 24 hours then spin evaporated to dryness in vacuum. Theresidue was dissolved in water and neutralized with NaHCO₃, extractedwith 2×50 ml of AcOEt, washed with water (2×) and the AcOEt extractfiltered through a siliconized filter and dried over MgSO₄. The driedsolution was filtered and spin evaporated in vacuum. Yellow oil, 2.8 g(52%). SGTLC in acetone Rf 0.8. HPLC Bondapak μC₁₈ MeOH/H₂ O (75:25) pH4 (formic acid). Elemental Analysis Calc. for C₁₆ H₁₇ NO₃. Calc. C70.83, H 6.32, N 5.16; Found C 70.77, H 6.47, N 5.04, 5.26.

EXAMPLE 3 4-Aminobenzilate of 3-(R,S)-quinuclidinol

5.16 g (40 mmol) of 3-(R,S)-quinuclidinol was dissolved in 50 ml of drybenzene and 20 ml of benzene distilled off. A clean 100 mg piece ofsodium was added and the suspension magnetically stirred, protected frommoisture and CO₂ (NaOH trap), and refluxed for 24 hours. 2.8 g (10.3mmol) of ethyl 4-aminobenzilate was dissolved in 50 ml of dry benzeneand 20 ml of benzene removed by distillation.

Both solutions were combined and refluxed, protected from moisture andCO₂ for 24 hours. The solution was spin evaporated, the residuesuspended in water and extracted twice with 50 ml of AcOEt. The AcOEtextract was washed repeatedly with water, filtered through a siliconizedfilter paper and dried over MgSO₄. The dried solution was filtered andspin evaporated in vacuum. The residue was dissolved in CH₃ CN andcharged on a silica gel column (2.8×100 cm) eluted with CH₃ CN. Purefractions crystallized on standing. The product recrystallized from CH₃CN, 1.5 g (41%) white crystals; SGTLC n-butanol, acetic acid, water4:1:1, Rf 0.4; HPLC Bondapak μC₁₈ MeOH/H₂ O 40/60, pH 4 (formic acid).IR, UV, mass spec. were consistent with the structure of the product.Calc. for C₂₁ H₂₄ N₂ O₃. Calc. C 71.57, H 6.86, N 7.95; Found C 71.27, H6.87, N 8.19.

EXAMPLE 4 4-[2-(3-methylpiperid-1-yl)-1,2-diaza-ethylen-1-yl]-benzilateof 3-(R,S)-quinuclidinol

Sodium nitrite (75 mg, 1.08 mmol) was added to a cooled (0° C.) solutionof 190 mg (54 mmol) of 4-amino-QNB in 6 ml of 10% H SO and acetone(5:1). The mixture was stirred for 15 min. at 0° then treated with 65 mg(1.08 mmol) of urea.

The diazonimum salt slurry was added to a cooled (0° C.) solution of 536mg (5.4 mmol) of 3-methylpiperidine in 5 ml of water. The mixture wasstirred at 0° C. for 20 min. then made basic with 4 N NaOH to pH 12 andextracted with CHCl₃ (3×5 ml). The combined extracts were washedrepeatedly with water and dried over MgSO₄. The solution was filteredand spin evaporated in vacuum. The residue was extracted with petroleumether (3×10 ml) and the combined extracts evaporated and dried in highvacuum to remove the traces of 3-methylpiperidine. Obtained was 240 mg(96%) of viscous yellow oil. SGTLC in 2% NH₄ OH in MeOH, Rf 0.5. HPLCBondapak μC₁₈ 5 mM 1-hexanesulfonic acid pH 4 (H₂ SO₄) in MeOH/H O,60/40. UV, IR, mass spec. were consistent with the product structure.Elemental analysis for C₂₇ H.sub. 34 N₄ O₃.2H₂ O. Calc. 65.03, H 7.68, N11.23; Found C 65.35, H 7.44, N 10.62.

EXAMPLE 5 (R,S)-Quinuclidin-3-ol-4-iodobenzilate

A solution of 5 mg (11 μmol) of QNB-triazene and 1.6 mg (11 μmol) ofsodium iodide in 1 ml of trifluoroethanol was treated with 6.4 mg ofmethanesulfonic acid. The reaction mixture was heated on a water bathfor 45 min., cooled, 5 ml of water added and extracted with 2×5 ml ofAcOEt. The aqueous layer was then neutralized with 4 N NaOH andextracted with 3×5 ml of AcOEt. The organic layer was washed three timeswith 1 ml of water, filtered through a siliconized paper and dried overNa₂ SO₄. After spin evaporation in vacuum, a yield of 2.7 mg (54%) wasobtained as a yellow oil. UV, IR, mass spec. were consistent with theproduct structure. SGTLC in n-BuOH:AcOH:H O, 4:1:1, Bondapak μC₁₈ 5 mM1-octanesulfonic acid, pH 4, MeOH/H₂ O, 60/40.

EXAMPLE 6 (R,S)-Quinuclidin-3-ol-4-bromo or 4-iodo or 4-fluorobenzilate(radio nuclides)

The compounds are prepared using the above procedure to produce theiodobenzilate substituting sodium radioiodide or radiobromide ortetrabutyl ammonium radiofluoride for sodium iodide.

To prepare the protonated or quaternary derivative, the product ofExample 5 or 6 is dissolved in a solution of the appropriate salt oralkyl halide and recrystallized therefrom.

EXAMPLE 7

The radiohalogen containing compound is utilized for imaging as follows:

The radio labeled tracer (I-123-QNB) is injected intravenously in theamount of 1 to 10 mCi at a specific activity to exceed 1000 Ci/mmol.Images of the distribution of radioactivity in the target organ areobtained as a function of time and the data stored in a computer. Thedata is then analyzed using an appropriate pharmacokinetic model todetermine the concentration of receptors as a function of disease.Alternately, the information can be used to determine the blood flow tothe target organ. For positron-emitting radiotracers such as Br-75 andF-18, coincidence counting is used. The images are collected over 2hours and the target organ can be any locus of muscarinic cholinergicreceptors such as the brain, the heart or the pancreas.

EXAMPLE 8

The radiohalogen containing compound can be used for the radio assay oftissue as follows:

Heart microsomal preparations are obtained as described by Harden et al[Mol Pharmacol 12: 1-15, 1976]. The heart from a rabbit is removed afterthe animal has been killed by cervical dislocation under light etheranesthesia. The heart is dissected free from atria and large vessels,minced with scissors and homogenized in buffer using a BrinkmanPolytron. The homogenate is centrifuged at 10,000 g for 20 min. and thesupernatent discarded. The pellet is resuspended in buffer andrecentrifuged. The pellet is then suspended in buffer. This homegenateis centrifuged over a layer of 0.2 M sucrose above a layer of 1.72 Msucrose. Membranes are collected at the interface of the two sucroselayers and used immediately for the radio-receptor assay.

Aliquots of the muscarinic cholinergic receptor isolated above, I-125IQNB and the test drugs are incubated at 37° C. with agitation.Incubations are carried out routinely for 120 min. Each incubation isterminated within 10 sec. by filtering the suspension through a GF/Cglass fiber filter positioned over a vacuum flask. The filter is rinsedwith 10 ml of buffer. The filter is then counted in a NaI(Tl)scintillation counter. Specific binding is experimentally determinedfrom the difference between counts bound in the absence and presence of1 μM atropine.

This same procedure can be used for any of the radiohalide-labeledderivatives of the invention.

The preferred technetium 99m (Tc-99m) derivatives may be prepared bysynthesis of a 3-quinuclidinyl glycolate with a ligand capable ofchelating Tc-99m to form an intermediate chelating agent andsubsequently labeling the intermediate with Tc-99m by chelation.

Any chelating agent capable of forming the quiniclidinyl glycolate maybe utilized provided that the resulting intermediate product is (1)capable of chelating Tc-99m and that (2) the Tc-99m labeled compoundretains its muscarinic cholinergic receptor binding properties.

Preferred agents are those primary and secondary amine groups containingligands capable of reaction through the amino group thereof with anethynyl derivative of 3-quinuclidinyl glycolate via the Mannich reactionto yield the intermediate chelating agent. Exemplary of such amines arethe so-called macrocyclic amines such as cyclam[1,4,8,11-tetraazacyclotetradecane] or its derivatives and kethoxal-bis(thiosemicarbazone) (KTS).

The intermediate chelating agent is prepared according to the followingreaction scheme: ##STR5##

The value of x is not critical and may range from about one to aboutten.

The resulting intermediates are labeled with Tc-99m according tostandard chelating procedures utilizing the pertechnetate (i.e., ^(99m)TcO₄ ⁻) and a suitable reducing agent. [Troutner et al, J. Nucl. Med.21: 443-448, 1980 and Yokoyama et al, J. Nucl. Med. 17: 816-819, 1976].

The resulting 99m-Tc labeled derivatives have the following structuralformulas: ##STR6##

We claim:
 1. A compound of the formula:wherein R is aryl, alkyl,cycloalkyl, phenyl, cyclopentyl, cyclohexyl, a ligand containing Tc-99min chelated form or a ligand capable of chelating Tc-99m; R₁ is H orlower alkyl; X is in the ortho-, meta- or para-position, and is selectedfrom the group consisting of ¹²⁵ I, ¹²³ I, ¹²⁷ I, I, ¹⁸ F, ⁷⁵ Br, ⁷⁷ Br,NH₂, and ##STR7## wherein R₂ is in the 2, 3, or 4 position and isselected from the group consisting of H and lower alkyl, provided thatwhen R is a ligand capable of chelating Tc-99m or containing Tc-99m inchelated form, X is not a radioisotope and may also be H or lower alkyl;Z.sup.⊖ is an anion; or the free amine thereof; and *denotes anasymmetric carbon atom.
 2. A compound according to claim 1 of theformula: ##STR8## wherein R is phenyl, cyclopentyl or cyclohexyl,R₁ is Hor CH₃, I is in the ortho-, meta- or para-position, and Z.sup.⊖ is ananion; or the free amine form thereof.
 3. The compound of claim 2wherein said I is in the meta-position and R₁ is H.
 4. The compound ofclaim 2 wherein said I is in the meta-position and R₁ is CH₃.
 5. Thecompound of claim 2 wherein said I is in the para-position and R₁ is H.6. The compound of claim 2 wherein said I is in the para-position and R₁is CH₃.
 7. The compound of claim 2 wherein said I is in theortho-position and R₁ is H.
 8. The compound of claim 2 wherein said I isin the ortho-position and R₁ is CH₃.
 9. A compound according to claim 1of the formula: ##STR9## wherein R is phenyl, cyclopentyl orcyclohexyl,R₁ is H or CH₃, ¹² I is in the ortho-, meta- orpara-position, and Z.sup.⊖ is an anion; or the free amine form thereof.10. The compound of claim 9 wherein said ¹²⁵ I is in the meta-positionand R₁ is H.
 11. The compound of claim 9 wherein said ¹²⁵ I is in themeta-position and R₁ is CH₃.
 12. The compound of claim 9 wherein said¹²⁵ I is in the para-position and R₁ is H.
 13. The compound of claim 9wherein said ¹²⁵ I is in the para-position and R₁ is CH₃.
 14. Thecompound of claim 9 wherein said ¹²⁵ I is in the ortho-position and R₁is H.
 15. The compound of claim 9 wherein said ¹²⁵ I is in theortho-position and R₁ is CH₃.
 16. A compound according to claim 1 of theformula: ##STR10## wherein R is phenyl, cyclopentyl or cyclohexyl,R₁ isH or CH₃, ¹² I is in the ortho-, meta- or para-position, and Z.sup.⊖ isan anion; or the free amine form thereof.
 17. The compound of claim 16wherein said ¹²³ I is in the meta-position and R₁ is H.
 18. The compoundof claim 16 wherein said ¹²³ I is in the meta-position and R₁ is CH₃.19. The compound of claim 16 wherein said ¹²³ I is in the para-positionand R₁ is H.
 20. The compound of claim 16 wherein said ¹²³ I is in thepara-position and R₁ is CH₃.
 21. The compound of claim 16 wherein said¹²³ I is in the ortho-position and R₁ is H.
 22. The compound of claim 16wherein said ¹²³ I is in the ortho-position and R₁ is CH₃.
 23. Acompound according to claim 1 of the formula: ##STR11## wherein R isphenyl, cyclopentyl or cyclohexyl,R₁ is H or CH₃, ¹² I is in the ortho-,meta- or para-position, and Z.sup.⊖ is an anion; or the free amine formthereof.
 24. The compound of claim 23 wherein said ¹²⁷ I is in themeta-position and R₁ is H.
 25. The compound of claim 23 wherein said ¹²⁷I is in the meta-position and R₁ is CH₃.
 26. The compound of claim 23wherein said ¹²⁷ I is in the para-position and R₁ is H.
 27. The compoundof claim 23 wherein said ¹²⁷ I is in the para-position and R₁ is CH₃.28. The compound of claim 23 wherein said ¹²⁷ I is in the ortho-positionand R₁ is H.
 29. The compound of claim 23 wherein said ¹²⁷ I is in theortho-position and R₁ is CH₃.
 30. A compound according to claim 1 of theformula: ##STR12## wherein R is phenyl, cyclopentyl or cyclohexyl,R₁ isH or CH₃, ¹ F is in the ortho-, meta- or para-position, and Z.sup.⊖ isan anion; or the free amine form thereof.
 31. The compound of claim 30wherein said ¹⁸ F is in the meta-position and R₁ is H.
 32. The compoundof claim 30 wherein said ¹⁸ F is in the meta-position and R₁ is CH₃. 33.The compound of claim 30 wherein said ¹⁸ F is in the para-position andR₁ is H.
 34. The compound of claim 30 wherein said ¹⁸ F is in thepara-position and R₁ is CH₃.
 35. The compound of claim 30 wherein said¹⁸ F is in the ortho-position and R₁ is H.
 36. The compound of claim 30wherein said ¹⁸ F is in the ortho-position and R₁ is CH₃.
 37. A compoundaccording to claim 1 of the formula: ##STR13## wherein R is phenyl,cyclopentyl, or cyclohexyl,R₁ is H or CH₃, ⁷ Br is in the ortho-, meta-or para-position, and Z.sup.⊖ is an anion; or the free amine formthereof.
 38. The compound of claim 37 wherein said ⁷⁵ Br is in themeta-position and R₁ is H.
 39. The compound of claim 37 wherein said ⁷⁵Br is in the meta-position and R₁ is CH₃.
 40. The compound of claim 37wherein said ⁷⁵ Br is in the para-position and R₁ is H.
 41. The compoundof claim 37 wherein said ⁷⁵ Br is in the para-position and R₁ is CH₃.42. The compound of claim 37 wherein said ⁷⁵ Br is in the ortho-positionand R₁ is H.
 43. The compound of claim 37 wherein said ⁷⁵ Br is in theortho-position and R₁ is CH₃.
 44. A compound according to claim 1 of theformula: ##STR14## wherein R is phenyl, cyclopentyl or cyclohexyl,R₁ isH or CH₃ ⁷ Br is in the ortho-, meta- or para-position, and Z.sup.⊖ isan anion; or the free amine form thereof.
 45. The compound of claim 44wherein said ⁷⁷ Br is in the meta-position and R₁ is H.
 46. The compoundof claim 44 wherein said ⁷⁷ Br is in the meta-position and R₁ is CH₃.47. The compound of claim 44 wherein said ⁷⁷ Br is in the para-positionand R₁ is H.
 48. The compound of claim 44 wherein said ⁷⁷ Br is in thepara-position and R₁ is CH₃.
 49. The compound of claim 44 wherein said⁷⁷ Br is in the ortho-position and R₁ is H.
 50. The compound of claim 44wherein said ⁷⁷ Br is in the ortho-position and R₁ is CH₃.
 51. Acompound according to claim 1 of the formula: ##STR15## wherein R isphenyl, cyclopentyl or cyclohexyl,R₁ is H or CH₃, the triazene group isin the ortho-, meta- or para-position, R₂ is H or lower alkyl in the 2,3, or 4 position, and Z.sup.⊖ is an anion; or the free amine formthereof.
 52. The compound of claim 51 wherein said triazene group is inthe meta-position and R₁ is H.
 53. The compound of claim 51 wherein saidtriazene group is in the meta-position and R₁ is CH₃.
 54. The compoundof claim 51 wherein said triazene group is in the para-position and R₁is H.
 55. The compound of claim 51 wherein said triazene group is in thepara-position and R₁ is CH₃.
 56. The compound of claim 51 wherein saidtriazene group is in the ortho-position and R₁ is H.
 57. The compound ofclaim 51 wherein said triazene group is in the ortho-position and R₁ isCH₃.
 58. A compound according to claim 1 of the formula: ##STR16##wherein R is phenyl, cyclopentyl or cyclohexyl,R₁ is H or CH₃, NH₂ is inthe ortho-, meta- or para-position, and Z.sup.⊖ is an anion; or the freeamine form thereof.
 59. The compound of claim 55 wherein said NH₂ is inthe meta-position and R₁ is H.
 60. The compound of claim 58 wherein saidNH₂ is in the meta-position and R₁ is CH₃.
 61. The compound of claim 58wherein said NH₂ is in the para-position and R₁ is H.
 62. The compoundof claim 58 wherein said NH₂ is in the para-position and R₁ is CH₃. 63.The compound of claim 58 wherein said NH₂ is in the ortho-position andR₁ is H.
 64. The compound of claim 58 wherein said NH₂ is in theortho-position and R₁ is CH₃.
 65. A method of preparing a compound ofclaim 58 comprising reacting a derivative of an aminobenzilic acid witha quinuclidin-3-ol to produce a quinuclidinyl aminobenzilate.
 66. Amethod for preparing a compound of claim 51 comprising reacting aderivative of an aminobenzilic acid with a quinuclidin-3-ol to produce aquinuclidinyl aminobenzilate and converting the free amine group to atriazene group.
 67. A method for preparing a compound of claim 1comprising reacting a derivative of an aminobenzilic acid with aquinuclidin-3-ol to produce a quinuclidinyl aminobenzilate, convertingthe free amino group to a triazene group, reacting the triazenederivative with a halogenide or radiohalogenide to form 3-quinuclidinylhalo benzilate.
 68. A composition suitable for the assay of muscariniccholinergic receptors in tissue comprising a gamma-emitting radioisotopecontaining compound of claim 1 and a pharmaceutically acceptable carriertherefor.
 69. A composition of claim 68 wherein said gamma-emitter is¹²⁵ I.
 70. The composition of claim 68 wherein said gamma-emitter is ¹²³I.
 71. The composition of claim 68 wherein said gamma-emitter is ¹²⁷ I.72. The composition of claim 68 wherein said gamma-emitter is ¹⁸ F. 73.The composition of claim 68 wherein said gamma-emitter is ⁷⁵ Br.
 74. Thecomposition of claim 68 wherein said gamma-emitter is ⁷⁷ Br.
 75. Thecomposition of claim 68 wherein said gamma-emitter is Tc-99m.
 76. Acomposition in unit dosage form suitable for use in a method for theexternal imaging or radio-assay of tissue containing muscariniccholinergic receptors comprising a gamma-emitting radioisotopecontaining compound of claim 1 and a pharmaceutically acceptable carriertherefor.
 77. In a method for the external imaging of or the radio-assayof muscarinic cholinergic receptors in tissue wherein a compositioncomprising a gamma-emitting radio-isotope containing muscariniccholinergic receptor binding compound is administered to an animal orhuman patient and the gamma-emissions from the receptor-boundradio-isotope containing compound are converted to visible images of thetissue or are otherwise quantitatively analyzed to determine muscariniccholinergic receptor concentration in said tissue, the improvementwherein said administered compound is a gamma-emitting radioisotopecontaining compound of claim
 1. 78. The method of claim 77 wherein saidgamma-emitter is ¹²³ I.
 79. The method of claim 77 wherein saidgamma-emitter is ¹²⁵ I.
 80. The method of claim 80 wherein saidgamma-emitter is ¹²⁷ I.
 81. The method of claim 77 wherein saidgamma-emitter is ¹⁸ F.
 82. The method of claim 77 wherein saidgamma-emitter is ⁷⁵ Br.
 83. The method of claim 77 wherein saidgamma-emitter is ⁷⁷ Br.
 84. The method of claim 77 wherein saidgamma-emitter is Tc-99m.
 85. A compound according to claim 1 of theformula: ##STR17## wherein R is a ligand containing technetium-99m inchelated form or a ligand capable of chelating Tc-99m;R₁ is H or loweralkyl, X is in the ortho-, meta- or para-position and is either H orlower alkyl, and Z.sup.⊖ is an anion; or the free amine form thereof.86. A compound according to claim 1 having the formula: ##STR18##wherein x=one to ten.
 87. A compound according to claim 1 having theformula: ##STR19## wherein x=one to ten.
 88. A compound according toclaim 1 having the formula: ##STR20## wherein x=one to ten, and Tc isTc-99m.
 89. A compound according to claim 1 having the formula:##STR21## wherein x=one to ten, and Tc is Tc-99m.